diff --git a/core/lib/Drupal/Core/KeyValueStore/MemoryStorage.php b/core/lib/Drupal/Core/KeyValueStore/MemoryStorage.php
index e6e07ef..fec8a1e 100644
--- a/core/lib/Drupal/Core/KeyValueStore/MemoryStorage.php
+++ b/core/lib/Drupal/Core/KeyValueStore/MemoryStorage.php
@@ -20,6 +20,13 @@ class MemoryStorage extends StorageBase {
   protected $data = array();
 
   /**
+   * Overrides \Drupal\Core\KeyValueStore\StorageBase::__construct().
+   */
+  public function __construct($collection) {
+    $this->collection = $collection;
+  }
+
+  /**
    * Implements Drupal\Core\KeyValueStore\KeyValueStoreInterface::get().
    */
   public function get($key, $default = NULL) {
diff --git a/core/lib/Drupal/Core/KeyValueStore/StorageBase.php b/core/lib/Drupal/Core/KeyValueStore/StorageBase.php
index 8dc54e6..b302896 100644
--- a/core/lib/Drupal/Core/KeyValueStore/StorageBase.php
+++ b/core/lib/Drupal/Core/KeyValueStore/StorageBase.php
@@ -31,7 +31,7 @@
   /**
    * Implements Drupal\Core\KeyValueStore\KeyValueStoreInterface::__construct().
    */
-  public function __construct($collection, SerializationInterface $format = NULL) {
+  public function __construct($collection, SerializationInterface $format) {
     $this->collection = $collection;
     $this->format = $format;
   }